The present invention relates to singulating devices whereby a stack of sheet members, such as envelopes, are received by the device and, in a seriatim manner, a single envelope is withdrawn from the stack for downstream processing.
It is the objective of singulating sheet-feeding devices within a mail processing environment to efficiently withdraw the bottom most envelope from an envelope stack employing a singulating apparatus and either transport or hand-off the bottom most envelope for further processing. The efficiency of the singulating process is expressed in terms of the ability of the singulating apparatus to consistently singulate envelopes as a function of variation in envelope stack height and stack composition. Envelope stack composition refers to the degree of permissible variability between the individual envelope as to size and thickness.
It is known to provide such devices with a stack receiving tray. The tray generally includes forward urging rollers which act on the bottom most envelope. Because of the pressure applied to the bottom most envelopes by the weight of the envelope stack, thereby, increasing the friction forces between the bottom envelopes, it is known to provide a reverse belt assembly for overcoming the friction load of the bottom envelopes. In order to provide efficient singulation of the envelope stack, it is common to limit the stack size such that the developed friction forces between the bottom most envelopes does not exceed the separation force applied by the reverse belt assembly.